In some insulin dependent diabetics, even something like delaying a meal can make them hypoglycaemic. Take note of this if you ever invite a diabetic over for a meal or take them out for dinner. If they start sounding confused, woozy or worse, think about getting some kind of food into them quickly.
Don't forget that the diabetic may well have taken his/her dose of insulin before coming over and may end up too confused to remember to tell you to provide the food on time.